(40c) Investigation into Existing and a Novel Device Based on the Granudrum to Determine Stickiness Point Detection of Powders

Measuring the stickiness of powders in relation to their temperature and moisture content is of great importance in the production of powders, esp from liquids. Stickiness is very much related to the glass transition temperature of powders. Specifically in spray dryers, fluid bed and drum dryers, where heat is used to remove the water, one want to finish with a non-sticky powder. Also in coating related processes, the stickiness give valuable information on spray rates of the coating solution in relation to the maximum temperature and humidity in the coater that can be set to prevent the particles from sticking to each other. Also for proper packaging of powders, stickiness of powders need to be measured to prevent lump formation

In this presentation some old and some novel techniques will be discussed and the limitations of the techniques will be given. Dynamic Vapour Sorption (DVS), Differential Scanning Calorimetry (DSC), AntonPaar Rheometer, as well as a fluid bed tester.

A novel device has been developed based on moving powder. A modified Granudrum has been developed where at different temperatures the relative humidity is changed of the air that is purged through the drum, where the angle of repose and the cohesivity measurements indicate the sticky points of the powders.

The techniques will be compared using the same powders. There are differences found for the dynamic and static measurements used. Also the range of powders that can be tested per technique will be addressed.